Haemoglobin

Question 1

What is haemoglobin?

Answer 1

A globular protein with a quaternary structure found in red blood cells. Haemoglobin carries oxygen from the lungs around the body.

Question 2

Describe the structure of haemoglobin>

Answer 2

Globular, water soluble and consists of 4 different polypeptide chains & each carrying a haem group (quaternary structure).

Question 3

What allows haemoglobin to have a quaternary structure?

Answer 3

Haemoglobin contains four different polypeptide chains which allows it to have a quaternary structure.

Question 4

Desribe the role of haemoglobin

Answer 4

Present in red blood cells. Oxygen molecules bind to haem groups and carried around the body to where they needed in respiring tissues.

Question 5

What happenes when oxygen binds to haemoglobin?

Answer 5

Oxyhaemoglobin is formed.

Question 6

Name three factors affecting oxygen-haemoglobin binding.

Answer 6

• Partial pressure/ concentration of oxygen
• Partial pressure/ concentration of carbon dioxide
• Saturation of haemoglobin with oxygen

Question 7

How does partial pressure of oxygen affect affect oxygen-haemoglobin binding?

Answer 7

As partial pressure of Oxygen increases the affinity of haemoglobin for oxygen also increases, so oxygen binds tightly to haemoglobin. When partial pressue is low, oxygen is released from haemoglobin.

Question 8

How does partial pressure of carbon dioxide affect oxygen-haemoglobin binding?

Answer 8

As partial pressure of carbon dioxde increases the affinity, the conditions become acidic causing haemoglobin to change shape. The affinity of oxygen then decreases, so oxygen is releases from haemoglobin. (Known as The Bohr effect)

Question 9

How does saturation of with haemoglobin affect oxygen-haemoglobin binding?

Answer 9

It is hard for the first oxygen molecule to bind. Once it does, it changes it shape to make it easier for the second and third molecules to bind (postive cooperativity). It is then slightly harder for the fourth oxygen molecule to bind as there is a low chance of finding a binding site.

Question 10

Explain why oxygen binds to haemoglobin in the lungs?

Answer 10

• Partial pressure of oxygen is high
• Low concentration of carbon dioxide in the lungs, so affinity is high.
• Postive cooperativity (After the first oxygen molecules bind, bindings of subsequent molecules is easier.)

Question 11

What do oxygen dissociation curves show?

Answer 11

Saturation of haemoglobin with oxygen (in %), plotted against partial pressure of oxygen (in kPa). Curves further to the left show the haemoglobin has a higher
affinity for oxygen.

Question 12

What is 21% of oxygen in kPa?

Answer 12

21% oxygen = 21kPa

Question 13

How does carbon dioxide affect the position of an oxyhaemoglobin dissociation curve?

Answer 13

Curve shifts to the right because haemoglobin’s affinity for oxygen has decreased.

Question 14

What is cardiac output?

Answer 14

The volume of blood pumped by one ventricle of the heart in one minute

Question 15

How do you calculate cardiac output?

Answer 15

Cardiac output = heart rate x stroke volume

Question 16

What is cardiac output measured in?

Answer 16

Measured in dm3/min

Question 17

What is a haem group?

Answer 17

A prosthetic group that is attached to the protein contains an iron ion which makes haemoglobin red.

Question 18

What is the name given to haemoglobin that has bound to oxygen?

Answer 18

Oxyhaemoglobin

Question 19

What is Oxygen partial pressure?

Answer 19

The concentration of oxygen in the cells. pO2 is important in determining whether oxygen binds to haemoglobin.

Question 20

What is Carbon dioxide partial pressure?

Answer 20

The concentration of carbon dioxide in the cells.

Question 21

What does it mean when the Oxygen partial pressure is high? (pO2)

Answer 21

Haemoglobin has a high affinity for oxygen and oxygen binds to haemoglobin.

Question 22

What does it mean when Oxygen partial pressure is low?

Answer 22

Haemoglobin has a low affinity for oxygen and oxygen dissociates from haemoglobin.